I'm so sorry to learn of the loss you and your family have experienced in the death of this little boy. It's clear you cared deeply for Arthur and for his parents. I can't imagine what they are going through right now, but I can pray. May God comfort their hearts when they hurt and surround them with His love.
If they think it might ever be helpful, I'm with an organization called Focus on the Family who has chaplains who would be happy to talk with this family over the phone when things get tough. They can be reached by calling 1-800-A-FAMILY (1-800-232-6459) anytime between 6:00 A.M. to 8:00 P.M. (MT) Monday through Friday. We also have an article series called "Coping With Death and Grief"
that might be helpful for Michelle and Arthur to read through.
Be assured this family is in my thoughts and prayers.